Question

Controlled cell death via apoptosis is mediated, in part, by the release of Cytochrome C, a component of the electron transport chain, into the cytoplasm of the cell. Which organelle in the cell is impacted in cells undergoing this mode of apoptosis?

Answer 1

Answer: Mitochondria.

Cytochrome C is located in the intermembrane space of mitochondria. When apoptosis is induced via intrinsic pathway, the pro apoptotic proteins Bax and Bad will create pores in the mitochondrial membrane which leaks cytochrome C into the cytoplasm. This disrupts the electron transport chain in mitochondrial membrane and the ATP production by mitochondria. In the cytoplasm, Cytochrome C will bind with APAf-1 protein (apoptosis activating factor-1) and form a complex called apoptosome. This complex will cleave and activate the initator caspase 9 from procaspase 9 into active caspase 9. Caspase 9 will cleave and activate other procaspase 9 molecules.Activated caspase 9 will cleave and activate caspase 3 and 6 which are effector caspases and they in turn will execute the programmed cell death process.